<template>
  <div class="pagination">
    <button :disabled="pageNo==1" @click="$emit('getPageNo',pageNo-1)">上一页</button>
    <button v-if="startNumAndEndNum.start>1"  @click="$emit('getPageNo',1)" :class="{active:pageNo==1}"> 1</button>
    <button v-if="startNumAndEndNum.start>2">···</button>

    <!-- 中间 部分 -->
    <button v-for="(page,index) in startNumAndEndNum.end" :key="index" 
    v-if="page>=startNumAndEndNum.start"
     @click="$emit('getPageNo',page)" :class="{active:pageNo==page}">{{page}}</button>
   


    <!-- 下 -->
    <button v-if ="startNumAndEndNum.end<totalPage-1" >···</button>
    <button v-if="startNumAndEndNum.end<totalPage"  @click="$emit('getPageNo',totalPage)"
    :class="{active:pageNo==totalPage}">{{totalPage}}</button>
    <button :disabled="pageNo==totalPage" @click="$emit('getPageNo',pageNo+1)">下一页</button>
    
    <button style="margin-left: 30px">{{total}}</button>
    <h1>{{startNumAndEndNum}}</h1>
  </div>
</template>

<script>
  export default {
    name: "Pagination",
    props:['pageNo','pageSize','total','continues'],
    computed:{
        // 总共多少页
        totalPage(){
            // 向上取整 math.ceil()
            return Math.ceil(this.total/this.pageSize)
        },
        // 计算出连续的页码起始数字与结束数字
        startNumAndEndNum(){
            //定义两个变量存储起始数字和结束数字
            let start = 0;
            let end = 0;
            // 连续的页码数字是5 如果出现不正常现象【数据不够5页
            if(this.continues > this.totalPage){
                start  = 1
                end = this.totalPage
            }else{
                // 正常现象
            start = this.pageNo - parseInt(this.continues/2)
            end = this.pageNo + parseInt(this.continues/2)
                if(start<1){
                    start = 1
                    end = this.continues
                }
                if(end>this.totalPage){
                    end = this.totalPage
                }
            }
            return {start,end}
        }
    }
}
</script>

<style lang="less" scoped>
  .pagination {
      text-align: center;
    button {
      margin: 0 5px;
      background-color: #f4f4f5;
      color: #606266;
      outline: none;
      border-radius: 2px;
      padding: 0 4px;
      vertical-align: top;
      display: inline-block;
      font-size: 13px;
      min-width: 35.5px;
      height: 28px;
      line-height: 28px;
      cursor: pointer;
      box-sizing: border-box;
      text-align: center;
      border: 0;

      &[disabled] {
        color: #c0c4cc;
        cursor: not-allowed;
      }

      &.active {
        cursor: not-allowed;
        background-color: #409eff;
        color: #fff;
      }
    }
  }
  .active{
    background: skyblue;
  }
</style>
